The amount of energy produced by wind farms has increased significantly the last decade, especially in China, and it is expected that the increase will continue in the future. Today, wind farms are established onshore in regions where the wind speed is as low as about 5 m/s. However, in the future, there might be a shortage of regions where it is economically sound to establish wind farms due to low wind speed.
Some regions of the earth are waste lands with less fertile soil, such as deserts or desert-like regions and grassland or grassland-like regions where the amount of wind is so low that they are not suitable for establishing wind farms, but would be well-suited for establishing wind farms if wind were generated.
The problem to be solved by the present invention is to provide means for generating so to say artificial wind and thereby wind farms that are independent of so to say natural wind.
By the term artificial wind is to be understood wind that did not exist in the region in question until the wind-generating means was arranged in the region.
By natural wind is to be understood wind that is caused by natural phenomena of nature, for example where natural wind occurred in the region before and will also occur after establishing the artificial wind-generating means. Natural wind will therefore also be referred to as background wind in the following.
It is known that on sunny days, a sea breeze circulation may develop due to uneven heating of the sea and the land. During the day, the land 5 heats up more than the sea 6, whereby the air over land 5 will be warmer in a low altitude than the air over the sea 6 in low altitude, see FIG. 1. The warm air over the land 5 rises 1 causing low pressure LI at low altitude. Over the sea 6, high pressure HI will form at low altitude because of the colder air, and over the sea 6, air will descent 2 from a low pressure Lh aloft i.e. at high altitude. At low altitude, wind will blow from the higher pressure HI at the sea 6 to the lower pressure LI over land causing a sea breeze 3. The rising air 1 over land is cooled, thus forming an area of high pressure Hh aloft. At this level, the air pressure and air density are higher than at the same level over the sea where the pressure as mentioned is low, whereby a return flow 4 is formed aloft in opposite direction of the sea breeze 3 and the sea breeze circulation completed.
Another and slightly different explanation of how a sea breeze or lake breeze is initiated is as follows:                the solar radiation heats the air above land 5, and the air above the sea 6 is cooled,        the air above the sea contracts, and the air above land expands,        at an altitude the pressure Hh above land is higher than the pressure Lh above the sea.        As a result of this horizontal pressure gradient, air flows from above land to above sea. This flow is called the return current 4.        the divergence of air above land causes the surface air pressure over land LI to drop, and convergence of air into the region above the sea causes the surface air pressure HI over the sea to increase,        the pressure difference at sea surface and at land surface initiates the sea breeze 3.        
The difference between the two explanations of the initiation of the sea breeze is whether it is initiated at surface level or at high altitude. Independent of the explanation, the result is that a sea breeze is formed due to different heating of the air above land and above the sea.
The present invention is explained by using the first mentioned explanation of how the sea or lake breeze is initiated. It should however be understood that independent of how the sea or lake breeze is formed, the effect of the present invention is the generation of artificial wind comparable to a sea or lake breeze, and also comparable to a so-called city breeze between a city essentially not heated during the day and an adjacent city heated during the day, and a breeze between two land regions, one being essentially not heated and the other being heated during the day.
From US 2010/0260925 it is further known to increase the terrestrial albedo by applying to the surface of the earth a reflective particulate material.
Further, US 2012/0175427 discloses cooling a land region by means of artificial clouds and heating another land region by means of other artificial clouds in order to cause a wind strengthening from the cooled to the heated region, wind turbines being arranged in the strengthened wind, cf. paragraph [0121].
By the term albedo or reflection coefficient is to be understood the ratio between the energy from the sun radiation reflected from a surface and the incident energy from the sun radiation upon the surface. The albedo is zero for no reflection from a perfectly black surface and 1 for a perfect reflection of a white surface.